Cytological studies have shown that for a number of coffee (Coffea spp.) genotypes, the resistance to H. vastatrix is characterized by restricted fungal growth (pre- or post-haustorial resistance) associated with several plant responses, such as rapid localized plant cell death (hypersensitive reaction), haustoria encasement with callose and b-1,4-glucans, deposition of phenolic-like compounds (such as chlorogenic acids), plant cell wall lignification, and plant cell hypertrophy. Some of these responses are also observed in susceptible plants, but occurred too late to prevent fungal growth and sporulation.
 

Biochemical studies revealed that the resistance is associated with the increase of activity of different oxidative enzymes e.g., peroxidase, superoxide dismutase and germin-like protein, as well as phenylalanine ammonia-lyase and chitinases. In the susceptible reaction some of these enzymes are also increased but later (or slower) in the infection process and, therefore, are ineffective to arrest the pathogen. Several genes putatively involved in signaling, recognition and defence were also identified in Coffea spp.-H. vastatrix interactions, including receptor kinases, WRKY, glucosyltransferases, lipoxygenases, and PRs (pathogen related genes). Salicylic acid (SA) quantification by HPLC/ESI-MS/MS showed an increase in this signaling compound at 24 hai in the incompatible interaction, suggesting the involvement of an SA-dependent pathway in coffee resistant to H. vastatrix.
 

A proteomic analysis (based on 2D electrophoresis) of the leaf apoplastic fluid (APF) of C. arabica-H. vastatrix interactions (resistant and susceptible) showed two distinct phases of defense responses, an initial/basal (at 24-48 hai) and a late/specific (at 72-96 hai). Compared to susceptibility, resistance was associated with a higher number of proteins, which was more evident in the late/specific phase. The identified proteins were mainly involved in proteins degradation, cell wall metabolism and stress/defense response. Furthermore, 70% of the identified proteins were hydrolases, mainly from sugars and peptides. Results obtained suggest that some glycohydrolases, proteases and PR-proteins are putative candidates for resistant markers of coffee to H. vastatrix.
 

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